Movement is directional about specific joints. In the upper body, the joint that moves in the most planes (3) is also the joint controlled by the largest and most muscles, which means that in seated aerobics, the shoulder joint will be the most used joint. Movement at the shoulder recruits the largest muscle mass, so movement at the shoulder will be essential for aerobic training. The important thing to remember when working the upper body muscles at the shoulder joint is to avoid overworking any set of the muscles, while not fully utilizing the other muscles.
The shoulder joint moves through three planes (Frontal, Saggital and Transverse (ACE)/Horizontal(AFAA)). The movements are:
NOTE: By seeing the same muscles of the shoulder used in different exercises, to avoid overstressing the Deltoid and the Lattissimus Dorsi, it would by good to include a sequence of exercises not using the Delt or the Lat between sets of forward and side lifting movements.
The Elbow Joint is a Hinge that moves in just one plane (the Sagittal Plane). Muscles in the upper arm control the Flexion/Extension of the Elbow Joint. These muscles are the Biceps Brachii and the Triceps. The Brachialis and the Brachioradialis are the assistor muscles on elbow Flexion.
The Radioulnar Joint has single plane movement (the Horizontal Plane). The Brachioradialis controls the Supination/Pronation movement.
The Wrist Joint, if separated in mechanics from the Radioulnar Joint, only moves in Flexion or Extension. Wrist Flexors are the primary muscles in Flexion and Wrist Extensors are the primary muscles in Extension.